It is already well known for grinding coffee to use a device which comprises two annular grinders mounted in opposition, one being fixed and the other being rotary, and in which the centrifugal force propels the ground coffee beans toward the periphery of the grinders where an opening is provided for recovering the coffee powder.
Almost all the modern automatic coffee machines comprise an integrated mill of the above-mentioned type. However, most of these machines are intended for working with two different kinds of coffee, the second kind being for example a caffeine free coffee. In this case, it is presently necessary to provide the coffee machine with two separated mills, that is for each with a feeding device, a body with annular grinders and a driving motor of the rotary grinder. This leads to the drawbacks on one part of necessitating a machine of larger sizes and on the other part of constituting a relatively expensive solution.